linux-ext4 - Re: [RFC 0/7] ext4: Allocator changes for atomic write support with DIO

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Date: Tue, 12 Dec 2023 10:16:13 -0500
From: "Theodore Ts'o" <tytso@....edu>
To: Christoph Hellwig <hch@...radead.org>
Cc: John Garry <john.g.garry@...cle.com>,
        Ojaswin Mujoo <ojaswin@...ux.ibm.com>, linux-ext4@...r.kernel.org,
        Ritesh Harjani <ritesh.list@...il.com>, linux-kernel@...r.kernel.org,
        "Darrick J . Wong" <djwong@...nel.org>, linux-block@...r.kernel.org,
        linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        dchinner@...hat.com
Subject: Re: [RFC 0/7] ext4: Allocator changes for atomic write support with
 DIO

On Tue, Dec 12, 2023 at 05:10:42AM -0800, Christoph Hellwig wrote:
> On Tue, Dec 12, 2023 at 07:46:51AM +0000, John Garry wrote:
> > It is assumed that the user will fallocate/dd the complete file before
> > issuing atomic writes, and we will have extent alignment and length as
> > required.
> 
> I don't think that's a long time maintainable usage model.

For databases that are trying to use this to significantly improve
their performance by eliminating double writes, the allocation and
writes are being done by a single process.  So for *that* use case, it
is quite maintainable.

Cheers,

						- Ted